20897551 has 2 divisors, whose sum is σ = 20897552. Its totient is φ = 20897550.

The previous prime is 20897543. The next prime is 20897557. The reversal of 20897551 is 15579802.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20897551 - 2³ = 20897543 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20897551.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20897557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10448775 + 10448776.

It is an arithmetic number, because the mean of its divisors is an integer number (10448776).

Almost surely, 2^20897551 is an apocalyptic number.

20897551 is a deficient number, since it is larger than the sum of its proper divisors (1).

20897551 is an equidigital number, since it uses as much as digits as its factorization.

20897551 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 25200, while the sum is 37.

The square root of 20897551 is about 4571.3839261213. The cubic root of 20897551 is about 275.4430368295.

The spelling of 20897551 in words is "twenty million, eight hundred ninety-seven thousand, five hundred fifty-one".